4.10 SCANPST-first aid for PSTs and OSTs

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ESEUTIL and ISINTEG are available to maintain the contents of server-based stores. There is also a need to ensure that users can fix any inconsistencies in local OST and PST files that occur through normal operation. Even when errors exist in their structure, the files might continue to work in an apparently normal manner, but eventually a problem becomes apparent.

Over time, you can expect that Outlook and Exchange (or vice versa) will experience communications failure. Network interruptions will occur, there may be errors reading or writing data to the hard disk, or you might find that someone powered off a PC while Outlook was running with an open PST or OST. Most of the problems that I have encountered with OSTs (as obvious in this chapter, I do not like PSTs very much) have occurred because a network connection terminated during synchronization.

If a fundamental problem occurs with an OST and you find that Outlook cannot read the file, the easiest solution is to recreate the file. Unlike a PST, it is easy to recreate an OST, albeit with some minor problems. After you restore or replace the disk, use Outlook's Tools | Services option to access the properties of the Exchange service. The Advanced tab allows you to define the name of a new OST. Enter a name or accept the default and click on OK. Outlook then creates the file, but you have to reconnect to Outlook before you can use the new file. A hidden benefit is that if you use Outlook 2003 and connect to an Exchange 2003 server, Outlook creates a unicode-based file, but only if you recreate your profile.

However, recreating an OST removes the folder properties controlling whether a folder is available offline for all folders except the special folders (Inbox, Calendar, and so on). Before synchronizing the other folders (including public folder favorites), you must mark each folder you want to use in offline mode and apply any necessary filters. Alternatively, you can use Outlook 2003 and a fully cached mailbox, which means that Outlook synchronizes all folders automatically. Obviously, synchronizing a brand new OST can take a long time, especially with a large mailbox or over a dial-in connection.

You need to rebuild the OST any time you get a new laptop PC. If you do rebuild a PC, remember that you also need to download the OAB to create the complete offline environment. As discussed earlier, some OABs are very large (HP's is over 183 MB when uncompressed), so this operation can take some time to complete.

Figure 4.38: The result of scanning an offline store.

Problems in a PST take on a different dimension, because the folders in a PST are not slave replicas of online folders so the data does not exist elsewhere. Instead, they are the sole containers for the data they hold. A tool that is able to "fix" a PST to get around the problem is, therefore, an important weapon in an implementation team's armory. That tool is SCANPST.EXE, and you find it in the same directory as the MAPI client software.^[7]

You can only run SCANPST if the program can gain exclusive access to the PST or OST you want it to process. After SCANPST opens the target file, it performs a series of eight tests to establish whether any inconsistencies exist in the internal structure of the file and the links between folders and items stored within. If SCANPST detects any inconsistencies, you can proceed to repair the file, or, in the case of a successful run, the program reports the number of items processed and will go no further. Mostly, as in the case shown in Figure 4.38, SCANPST finds errors and there is no option but to carry on and repair the file. In this instance, my OST is large (20,628 items in a 650-MB file) and had been in continual use for over four months, so it was not too surprising to find that a few errors had crept in. SCANPST offers to detail the problems within a file, but, as you can see, the detailed information that the utility presents is hardly enlightening!

SCANPST creates a small log file in the same directory as the PST or OST that you have processed. While the file reveals some of the processing done by SCANPST, it is not too revealing either. Because Outlook 2003 depends on an OST to implement its cached Exchange mode, it runs code to validate that the local cache is consistent every time you start the client. If Outlook detects that the local cache is inconsistent for some reason (again, network interruptions of forced client shutdowns commonly lead to inconsistencies), it attempts to make the cache consistent by checking the contents of the OST, validating the local indexes, and ensuring that the correct links exist between tables. While this happens, you have an opportunity to get an extra cup of coffee. Figure 4.39 shows why.

Figure 4.39: Checking for OST errors.

In general, there is no need to run SCANPST unless you find a problem with either a PST or OST. But there is no harm in running the program, and it does provide a certain peace of mind for those of us who form the more paranoid element of the Exchange community.

4.10.1 The value of an OST

I can live without PSTs, but the loss of offline capability would severely affect my daily working life. Before Outlook 2003, my OST typically contained between 20,000 and 30,000 items in a variety of folders and occupied up to 650 MB of disk space. I am certainly not the record holder in this respect, since I know of people who keep hundreds of thousands of items offline, using more than 3 GB of space. Now, with Outlook 2003's cached Exchange mode, my OST is much larger because it holds a complete copy of my mailbox and all my public folder favorites, so the OST is even more useful.

With all versions of Outlook, offline folders complement the client's dial-up capability and make it easier for road warriors to get their job done. Without the ability to browse and reply to messages offline, I would not have much chance of getting through the hundreds of messages I receive each week. Offline access also makes it much easier to keep up-to-date with the events in heavily trafficked distribution and mailing lists.

^[7] . On PCs running Windows XP Professional, the program can be found in \Program Files\Common Files\System\MAPI\NT.

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